1. Field of the Invention
The invention relates to a solenoid valve unit for shutting off or enabling a throughflow of a medium along a hollow duct, which flows along the hollow duct under application of pressure, having at least one first magnet unit which is fixedly arranged along the hollow duct and a second magnet unit, which is mounted so it is movable in relation to the first magnet unit, and which can be brought into indirect or direct contact with the first magnet unit on account of an attractive magnetic force prevailing between the two magnet units, and seals the hollow duct in a fluid-tight manner, while the medium loads the first magnet unit under application of pressure opposite to the action direction of the magnetic force.
2. Description of the Prior Art
Devices for the metered dispensing of viscous media, preferably low-viscosity, medium-viscosity, and high-viscosity liquids, such as oils, greases, adhesives, and soldering pastes, to name only a few, are often also known under the name “dispenser” and are used in greatly varying technical areas, such as precision engineering, nanotechnology, and microtechnology, and in particular, in the fields of microelectronics, microoptics, and micromechanics and also in biotechnology and medical technology. Typical applications of such dispenser systems for medium-viscosity and high-viscosity media relate, for example, to the exact dispensing and positioning of ultrasmall adhesive drops for joining in electronics manufacturing, the lubrication of bearings using oils and greases in mechanical engineering, preferably in the field of micromechanics, and the continuous or cyclic delivery of reagents in the chemical industry or for purposes of analysis technology or also for administering ultrafine dosed liquid pharmaceuticals for patient care, in particular in intensive medicine.
An overview of dispenser systems for medium-viscosity and high-viscosity media, which are capable in particular of generating and placing drops, so-called dots, in the context of cyclic dispensing of media, can be taken from an article by F. Kohler “Punkt für Punkt—Die Techniken für das Dispensen von Lotpasten [point for point—the technologies for the dispensing of solder pastes]”, published in “Productronic” (1991), issue 4, pages 18 to 20. In addition to the time/pressure cartridge dosing systems, rotation screw dosing systems, peristaltic dispensing systems, and piston positive displacement dosing systems described therein, solenoid valve systems are additionally known, whose valve mechanism is based on a mutual adaptation of prevailing magnetic forces to the flow or delivery pressure, which originates from a media flow to be dosed using the valve unit.
In this context, reference is made to DE 38 02 658 A1, in which a solenoid valve is described, whose mode of operation is determined by the axial position of a permanent magnet, which is mounted so it is movable axially relative to the hollow duct. On account of the magnetic conditions of the permanent magnets provided in the solenoid valve, the valve configuration remains open in a base position which is unloaded by external force actions, particularly on account the axially movable magnet unit experiencing an axially acting repelling force through the magnet unit which is also provided in the hollow duct. In contrast, if a corresponding axial flow pressure or volume flow acts on the valve seat, it is axially displaced and moved against a valve needle until the valve unit passes into a closed state upon reaching a maximum value flow. The known solenoid valve may be used in a particularly advantageous way as a magnetic regulating valve through the shaping of the valve body and the desired large longitudinal mobility of the valve seat in the axial direction. For these purposes, optical sensors are provided along the cavity wall, in order to detect the axial location of the valve seat.
An automatically operating shutoff valve, in particular for oil burners, is disclosed in EP 0 213 516, which is to prevent dripping of oil after ending the burning action. For this purpose, the shutoff valve provides a longitudinally-movable shutoff body, which entirely or partially comprises a permanent-magnetic material. In a starting state, the shutoff body is pressed in a fluid-tight manner on one side against the component, which is designated as the armature, and which has a central hole through which liquid oil is fed. If an oil flow is applied, it presses the shutoff body into an axially distant position from the armature while overcoming the magnetic retaining forces, so that an oil flow occurs through the oil nozzle. The shutoff body encloses an intermediate gap using the sleeve-type element which surrounds it.
A magnetic shutoff valve, which comprises a plate valve unit, which is combined with a permanent magnet, is disclosed in U.S. Pat. No. 5,320,136. In a starting state, the plate valve is located in a closed valve position through mutual magnetic attraction of the existing magnets, while in contrast when a flow pressure is applied to the plate valve and exceeds the magnetic retaining force, an axial deflection of the plate valve is caused, whereby the valve is opened.
A magnetic shutoff valve is disclosed in U.S. Pat. No. 3,026,903, in which a magnetic ball is mounted so it is axially movable inside a magnetic sleeve. In a starting state, the ball is located in an upper area and is in fluid-tight contact with a sealing disc. As soon as a medium flow is applied through the valve, the ball is deflected against the magnetic retaining force, whereby the shutoff valve opens.
Furthermore, a valve unit according to the species is disclosed in WO 2008/037430, which represents prior art published after the present application and represents the most similar prior art.